Quarter degree resolution ocean component of the Norwegian Earth System Model

Transcription

1 Quarter degree resolution ocean component of the Norwegian Earth System Model Mats Bentsen 1,2, Mehmet Ilicak 1,2, and Helge Drange 3,2 1 Uni, Uni Research Ltd 2 Bjerknes Centre for Research 3 Geophysical Institute, University of Bergen

2 Outline Summary of current state-of-the-art simulations. Scientific questions to be addressed by high-resolution simulations. Main challenges for the progress in high-resolution modelling. Questions we would like addressed during the meeting.

3 Tripolar grids 1 grid (every 4th grid line shown): grid cells. Used for the NorESM-O CORE2 experiments. Enhanced meridional resolution near the equator (fe = 1/4) grid (every 16th grid line shown): grid cells. Isotropic grid near equator. Target resolution for CMIP6 experiments.

4 Model configurations Grid Laplacian Smag. ν = (CΔ/π) 2 D Biharmonic Smag. ν = (B/π) 2 Δ 4 D Thickness diffusivity (m 2 s 1 ) κ = f(r d ) Tripolar 1 C = 0.5 B = ~ [1 + (R d /Δ) 4 ] 1 Tripolar 0.25 C = 0.15 B = ~ [1 + (R d /Δ) 4 ] 1 Tripolar 0.25 C = 0.5 B = ~ [1 + (R d /Δ) 4 ] 1 Tripolar 0.25 C = 0.5 B = ~ [1 + (R d /Δ) 4 ] 1 51 isopycnic layers, 2 layers in the mixed layer. CORE II inter-annual varying forcing. On Cray XE6: ~ 20 simulated years per day of 1 configuration using 123 pes and 60 pes for ocean and sea-ice, respectively. ~ 5-6 simulated years per day of 0.25 configuration using 1681 pes and 360 pes for ocean and sea-ice, respectively.

5 SSH variability of the South Atlantic and Atlantic sector of Southern Ocean 1 resolution 0.25 resolution

6 Eddy kinetic energy

7 Zonal Jets Derived from mean dynamic ocean topography. Courtesy: Maximenko et al. (2008). NorESM 0.25 ocean resolution.

8 Atlantic meridional overturning circulation

9 Atlantic Ocean zonal mean temperature bias 1 resolution 0.25 resolution

10 Scientific questions to be addressed by highresolution simulations What is the impact of partially resolved eddy transport in coupled climate simulations? What is the atmospheric impact of a less heterogeneous ocean/sea-ice surface? How can better resolved ocean circulation and sea-ice drift improve the representation of the Nordic Seas/Arctic Ocean? How does an improved representation of the North Atlantic subpolar region impact simulated climate variability? How does improved resolution impact ocean biogeochemistry? What is the impact of higher resolution on boundary currents and the representation of water masses in the vicinity of ice shelves.

11 Main challenges for the progress in highresolution modelling Computational/storage/analysis workflow challenges. Adequately handle processes that may be resolved or parameterized in the same computational domain. Due to the reduced simulation speed it is more challenging to tune model parameters.

12 Questions we would like addressed during the meeting What is the current state of art in resolution dependent parameterizations? Is the AMOC in other models sensitive to the resolution? Sensible methods for acceleration of the ocean biogeochemical spinup. Can higher order numerical methods extend the area of resolved eddy fluxes?

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14 Scalability of ocean component on a Cray XE simulated years per day cores

15 SSH variability of the North Atlantic 1 resolution 0.25 resolution

16 Meridional heat transport Q total = Q eddy + Q residual

17 Sea surface temperature error 1 rms= rms=0.75

18 Isopycnic diffusivity in 1 NorESM Thickness diffusivity is equal to isopycnic diffusivity. Tracer diffusivity (passive) is equal to thickness diffusivity.